Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Nullification Greathelm Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Nullification Greathelm suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Transmog Sets
Nullification Greathelm is part of the transmog set Gatecrasher's Battleplate (Warrior, Paladin and Death Knight only). The other 16 pieces:
Built from the World of Warcraft client build files and recorded Auction House snapshots.
Where Nullification Greathelm Fits
Other Items Named Nullification Greathelm
2 other items in the current build are also called Nullification Greathelm. Same-name entries are usually a different rank, faction, quest stage or reward track of the same object.
Blizzard numbers items as they are created, so the named items next to ID 86752 (86747 to 86757) were usually added in the same batch as Nullification Greathelm: the same quest line, zone, vendor or reward set.